Studying the Edge of the Heliosphere

NASA's Interstellar Mapping and Acceleration Probe (IMAP) mission, which APL is building in partnership with Principal Investigator David McComas of Princeton University, will enable a deeper understanding of the boundary of our heliosphere, the bubble carved in interstellar space by the Sun’s magnetic field that surrounds and protects our solar system.

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The heliosphere is filled with a constant flow of charged particles from the Sun, known as the solar wind, that collides with material from the rest of the galaxy and local interstellar medium at the heliospheric boundary. The Interstellar Mapping and Acceleration Probe (IMAP) mission will answer fundamental scientific questions about the local interstellar medium, the boundaries that surround our solar system and how particles are accelerated to high energies in space. For example, IMAP will reveal how cosmic rays are filtered by the heliosphere. These particles pose risks to astronauts and technological systems, but they may also play a role in the formation and presence of life in the universe.  

IMAP is the fifth NASA Solar Terrestrial Probes (STP) mission. IMAP moved into phase B in spring 2020. APL is performing spacecraft technology development, engineering prototyping, hardware and software capability and cost assessments, and other risk-mitigation activities. The instrument teams are procuring materials needed for their builds, and science teams are working on combined science observations.

Spacecraft and Instruments

The APL-built IMAP spacecraft will carry a suite of 10 science instruments provided by international and domestic research organizations and universities. The spacecraft will cruise to its final position about 1 million miles (1.5 million kilometers) in front of Earth at the first Sun-Earth Lagrange point, or L1. This stable orbit allows the probe to maximize use of its instruments to monitor the interactions between the solar wind and the interstellar medium in the outer solar system.

Mission Facts

February 2025

Principal Investigator
David McComas, Princeton University

Project Manager
John Scherrer, Johns Hopkins APL

Project Scientist
Joe Westlake, Johns Hopkins APL


Rendering of the IMPA Spacecraft
An interactive, 3D rendering of the IMAP spacecraft. Click on the image and drag to see all angles of the spacecraft.

Learn More About Instrument(s) on this Mission